Proper securing of a parked vehicle to a loading dock during a loading or unloading operation is an essential safety precaution. Various restraints have heretofore been provided to accomplish the desired result by having a portion thereof engaging an ICC bar depending from the rear of the parked vehicle. By reason of the condition of the ICC bar and/or the weight of the load being carried by the vehicle, the height of the ICC bar relative to the roadway may vary 15 or more inches. Thus, where the restraint incorporates a vertically adjustable carriage member, such as disclosed in U.S. Pat. No. 4,264,259, which is adapted to be engaged by the ICC bar of the vehicle while the latter is backing into position, the carriage member will automatically move downwardly from its upwardly biased rest position the required amount so that the attaching member (hook) mounted on the carriage member can lockingly engage the ICC bar. Heretofore, where the height of the ICC bar was less than 15 inches above the roadway, difficulty was experienced in some instances in that the ICC bar did not engage the cam surface of the carriage member, and thus, the attaching member was not able to engage the ICC bar. In other instances where the carriage member was forced to move downwardly to the fullest extent by the ICC bar of the backing vehicle the bar was forced to move upwardly over the cam surface of the carriage member causing the restraint, the dock wall to which it is attached, as well as the vehicle ICC bar to be subjected to damaging and/or severe stress and strain.